I have once collected information from tuning provider pages and forum entries and think that the following values could be quite realistic (5th driving stage) – also depending on the respective PS difference. The tolerances can be high with the Smart due to wind influences and other tyres, should be clear. 61hp: 145-150 km/h 71hp (+10hp): 150-155 km/h 84hp (+13hp): 160-165 km/h 105hp (+21hp): 175-185 km/h (“small” performance increase) 117hp (+12hp): 185-195 km/h (“big” performance peak) I don’t want to pursue a “tail extension” discussion here (“my is faster”, it should only be about clues on which one can orient oneself so roughly. Nevertheless, other experience values are interesting if measured with GPS and not downhill or with tailwind.